Authors:Yue Sun; Zhixiang Shi Tsuyoshi TamegaiFirst page: 103001Abstract: Among iron-based superconductors, Fe 1+ y Te 1− x Se x is unique in its structural simplicity,
consisting of only FeTe/Se layers, which is favorable for probing the mechanism of
superconductivity. Recently, a topological surface superconductivity as well as Majorana fermions
has been observed, which makes Fe 1+ y Te 1− x Se x the first high-temperature topological
superconductor. Thus, Fe 1+ y Te 1− x Se x is unique for the study of both high temperature and
topological superconductivities. Since the large size single crystal of Fe 1+ y Te 1− x Se x can be
easily grown, much research has been performed. However, a large number of the reported results are
controversial, or differ between groups, including those related to basic properties such as
resistivity, susceptibility, the ...Citation: Superconductor Science and TechnologyPubDate: 2019-08-21T23:00:00ZDOI: 10.1088/1361-6668/ab30c2Issue No:Vol. 32, No. 10 (2019)

Authors:Hyung-Seop ShinFirst page: 104001Abstract: The performance characteristics of second-generation rare-earth barium copper oxide-coated conductor
(CC) tapes are influenced by stress and strain induced during fabrication, cool-down, and operation.
Electromechanical characteristics have been improved using several methods such as adding a
stabilizer and external lamination. In multilayered structures such as CC tapes, structural
delamination or ballooning phenomenon can occur in the interlayers. In particular, when CC tapes are
applied to magnets or coils under a high field magnet, delamination is a critical damage. Therefore,
it is important to examine the failure behaviors of CC tapes under transverse tension load and to
evaluate the delamination characteristics. In this study, anvil test methods were used to
mechanically and electromechanically investigate the delamination characteristics of CC tapes
processed by reactive co-evaporation by deposition and reaction under transverse tension load at 77
K and a self-field. To ...Citation: Superconductor Science and TechnologyPubDate: 2019-08-20T23:00:00ZDOI: 10.1088/1361-6668/ab3151Issue No:Vol. 32, No. 10 (2019)

Authors:Facundo Sosa-Rey; Frédéric Sirois, Christian Lacroix Charles-Henri BonnardFirst page: 105005Abstract: High temperature superconducting coated conductors (CCs) are wires with ideal nonlinear properties
for use as resistive superconducting fault current limiters (rSFCLs) for power systems. However,
choosing a conductor architecture that can survive all types of excitations occurring in a specific
power system is a big challenge. Firstly, the non-uniformity of the critical current along the
length of commercial CCs makes them prone to hot spots. Secondly, the current flowing in a CC-based
rSFCL is determined by the specific dynamics of the power system in which it is installed. In order
to correctly design the CC architecture, one must be able to compute the electrothermal bevahiour of
CCs submitted to realistic power system excitations. This requires coupling a
physically-representative CC model with a suitable commercial power system simulator. In this paper,
an example of such coupling is presented, with the particularity that the numerical method used to
simulate CCs can accoun...Citation: Superconductor Science and TechnologyPubDate: 2019-08-21T23:00:00ZDOI: 10.1088/1361-6668/ab2e67Issue No:Vol. 32, No. 10 (2019)

Authors:R Gyuráki; T Benkel, F Schreiner, F Sirois F GrilliFirst page: 105006Abstract: We have wound a 157-turn, non-insulated pancake coil with an outer diameter of 85 mm and we cooled
it down to 77 K with a combination of conduction and gas cooling. Using high-speed fluorescent
thermal imaging in combination with electrical measurements we have investigated the coil under
load, including various ramping tests and over-current experiments. We have found that the coil does
not heat up measurably when being ramped to below its critical current. Two over-current experiments
are presented, where in one case the coil recovered by itself and in another case a thermal runaway
occurred. We have recorded heating in the bulk of the windings due to local defects, however the
coil remained cryostable even during some over-critical conditions and heated only to about 82–85 K
at certain positions. A thermal runaway was observed at the center, where the highest magnetic field
and a resistive joint create a natural defect. The maximum temperature, ∼100 K, was reached only in
the...Citation: Superconductor Science and TechnologyPubDate: 2019-08-21T23:00:00ZDOI: 10.1088/1361-6668/ab38f2Issue No:Vol. 32, No. 10 (2019)

Authors:G P Papari; V M FominFirst page: 105008Abstract: We propose a mean-field approach to describe the fluxoid dependence of magnetoresistance
oscillations measured on two YBa 2 Cu 3 O 7− x (YBCO) nanorings. We unveil the relation between the
quantum interference processes and current localization phenomena in superconductor nanorings, which
are non-ideal because of the presence of stubs. The model, based on the change in supercurrent
transmission due to fluxoid dynamics, provides a dependence of the measured differential voltage on
the external magnetic field. In particular, the signature of the Little and Parks (LP) effect
results from phase dynamics involving the transmission of probe currents crossing the ring, while
magnetoresistance background is related to the screening currents dynamics driven by vortex
nucleation. The model allows for tracing out the entire magnetoresistance, which is the result of
the superposition of single vortex-like topological defects involving current localization....Citation: Superconductor Science and TechnologyPubDate: 2019-08-26T23:00:00ZDOI: 10.1088/1361-6668/ab315fIssue No:Vol. 32, No. 10 (2019)

Authors:M Rosmus; R Kurleto, D J Gawryluk, J Goraus, M Z Cieplak P StarowiczFirst page: 105009Abstract: Angle-resolved photoemission spectroscopy reveals the effects of electron doping, which is realized
by Co and Ni substitution for Fe in a FeTe 1− y Se y (y ∼ 0.35) superconductor. The data show
consistent band shifts as well as expansion and shrinking of the electron and hole Fermi surface,
respectively. Doping of either element leads to a Lifshitz transition realized as a removal of one
or two hole pockets. This qualitatively explains the complex behavior of the Hall coefficient
observed previously (Bezusyy et al , 2015 Phys. Rev. B 91 , 100502), including the change of sign
with doping, which takes place only below room temperature. Assuming that Ni substitution should
deliver twice as many electrons to the valence band as Co, it appears that such transfer is slightly
more effective in the case of Co. Therefore, charge doping cannot account for a much stronger effect
of Ni on the superconducting and transport properties (Be...Citation: Superconductor Science and TechnologyPubDate: 2019-08-26T23:00:00ZDOI: 10.1088/1361-6668/ab324fIssue No:Vol. 32, No. 10 (2019)